A nuclear event energy detector is an instrument that converts amplitudes of nuclear radiation pulses into measurable electrical signals and measures the electrical signals. The electrical signals are a series of discrete pulse signals, and the amplitude values of these pulse signals represent energy of the radiations. A conventional method for measuring the amplitude of a nuclear radiation pulse signal includes converting the input analog signal into digital format using an analog-to-digital converter (ADC). This method is inapplicable to a nuclear detector system with a large number of channels and requiring parallel readout of multiple channels, such as a nuclear imaging detector system. This is because each of the channels needs a high-speed ADC, leading to an unacceptable scale of an electronic system for signal readout and digitization. There is therefore a need for a new method for amplitude digitization of a nuclear radiation pulse to accommodate the parallel readout and digitization requirements for a system with a large number of channels while achieving a high integration level.